A condition sometimes encountered in a pumping well when dissolved gas, released from solution during the upstroke of the plunger, appears as free gas between the valves. On the downstroke, pressure inside a barrel completely filled with gas may never reach the pressure needed to open the traveling valve. In the upstroke, the pressure inside the barrel never decreases enough for the standing valve to open and allow liquid to enter the pump. Thus no fluid enters or leaves the pump, and the pump is locked. It does not cause equipment failure, but with a nonfunctional pump, the pumping system is useless.A decrease in pumping rate is accompanied by an increase of bottomhole pressure (or fluid level in the annulus). In many cases of gas lock, this increase in bottomhole pressure can exceed the pressure in the barrel and liquid can enter through the standing valve. After a few strokes, enough liquid enters the pump that the gas lock in broken, and the pump functions normally.

Related Terms:

gas separator
traveling valve